1. Field of the Invention
The present invention relates to audio equipment and a method of controlling audio equipment, in particular, to a system having a switching type power amplifier circuit. According to the present invention, by varying a switching frequency of a power amplifier circuit in accordance with a receiving frequency, a user can surely listen to a desired program in a case where the audio system includes a switching power amplifier circuit.
2. Description of Related Art
In conventional audio equipment, a power amplifier circuit drives a speaker. The power amplifier circuit is sorted into two types: a linear power amplifier in which an input signal is linearly amplified, and a switching power amplifier in which a final transistor is switched in accordance with a pulse width modulation signal generated from an input signal.
In late years, the switching power amplifier circuit (so-called “class D power amplifier circuit) is employed in audio equipment including a car audio system or the like, since it has higher power efficiency and less heat emission compared to the linear power amplifier.